Ozone exposure (in concentrations at or near the current ambient air quality standard: 120 ppb) results in airway epithelial cell injury and inflammation. When inhaled, ozone reacts with phospholipids and proteins in the extracellular fluid or the plasma membrane. We hypothesize that a portion of ozone's toxicity is due to secondary reaction products that, in turn, have biological activity. We propose that these reaction products can activate constitutive airway cells and lead to the synthesis and release of mediators including eicosanoids and cytokines. These mediators have biological activities important to the mechanisms of ozone toxicity in the lung through their modulatory effects on ion transport and mucus secretion (local responses) and inflammation and possibly smooth muscle tone (systemic responses). One macromolecular site of ozone attack is the carbon-carbon double bonds in unsaturated fatty acids (molecules present in the extracellular lining fluid and plasma membrane). Ozonolysis of unsaturated fatty acids leads principally to the formation of 3-, 6-, or 9-carbon aldehydes and hydroxyhydroperoxides. In aqueous environments, the hydroxyhydroperoxides can subsequently degrade into another aldehyde and hydrogen peroxide. The specific aims of this proposal are: (1) to synthesize and purify 3-, 6-, 9-carbon saturated and unsaturated aldehydes and hydroxyhydroperoxides, and (2) to investigate the effects of these compounds (and hydrogen peroxide) on eicosanoid and cytokine release from human airway epithelial cells. This study is designed to provide evidence to evaluate the relative toxicity of ozonolysis intermediates and the role of epithelial-derived mediators in ozone-induced airway inflammation. These findings will be helpful in explaining why ozone (which is very reactive and unlikely to penetrate the apical membrane of the airway epithelium) can initiate effects distant to the site of ozone- macromolecule chemical interactions.